1. Field of the Invention
The present invention relates to an image forming apparatus and a method for controlling the same, and more particularly, relates to an image forming apparatus including heating units for heating photosensitive drums, heat rollers, etc. and a method for controlling the same.
2. Description of the Related Art
As will be explained below in reference to the attached drawings, a conventional image forming apparatus is basically comprised of a power switch for instructing turning on and off of power, heating units for heating photosensitive drums, heat rollers, etc. and requiring power before printing, a machine unit provided with a conveyance system for paper, photosensitive drums, heat rollers, and various other mechanisms used for printing, and a power control unit for turning on or turning off the power based on the instruction from the power switch. The power control unit does not supply power to any unit other than the heating units, that is, the conveyance system and the rest of the machine unit, but continues to supply power to the heating units even when instructed to turn off power to the apparatus as a whole.
In the afore mentioned conventional image forming apparatus, power continues to be fed to the heating units throughout the night (all day) even after the power to the apparatus as a whole is turned off by the power switch. This is because the heating units have to heat drums or other objects with a larger calorific capacity and once the heat dissipates it takes time to return to the service temperature. This would mean an inability of immediate operation of the apparatus for printing and would be inconvenient to the user.
Accordingly, it is necessary to supply power throughout the night. Since the heating units are powered through the night, there have been safety problems and a large energy consumption.
On the other hand, when linking the turning on and off of power to the heating units with the turning on and off of power to the apparatus as a whole, it is necessary to turn on the power of the apparatus as a whole a predetermined time prior to one starting the printing in view of the time needed for the heating units to heat up the photosensitive drums. This means inconvenience in service due to the time gap between when the power is turned on and the time gap between when service may begin (Users generally want to be able to start using a machine right after they turn on the power.) Also, power is supplied to the apparatus as a whole, not only the heating units, during the warmup period. The power consumption is therefore that much larger compared to the situation in which power is supplied only to the heating units.